Induction motor controller

ABSTRACT

A motor controller is capable of swiftly driving a motor at the initial stage and driving the motor with high efficiency and low power consumption after swiftly driving the motor at the initial stage by including a first capacitor connected in series with a common terminal to which the main coils and the sub-coils of the motor are connected and a PTC thermistor (Positive Temperature Coefficient thermistor) connected in parallel with the first capacitor.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an induction motor, and particularly,to an induction motor controller.

2. Description of the Conventional Art

FIG. 1 is a view schematically showing a construction of an inductionmotor in accordance with the conventional art.

As shown in FIG. 1, the induction motor in accordance with theconventional art largely includes: a stator 100; an induction rotor 120;a permanent magnet rotor 140; and a rotating shaft 110.

The stator 100 is made up of main coils 160A and 160B and sub-coils 160Cand 160D respectively wound around an iron core 150 of the inductionmotor. Here, the main coils 160A and 160B and the sub-coils 160C and160D are sequentially connected in series such that the coils adjacentto each other have the same polarities.

The permanent magnet rotor 140 consists of a ring type permanent magnet(not shown) installed between the stator 100 and the induction rotor 120at a predetermined gap and a permanent magnet supporting unit (notshown) for supporting the ring type permanent magnet. Also, to make thepermanent magnet rotor 140 rotated centering around the rotating shaft110, a bearing 130 is installed between the permanent magnet supportingunit and the rotating shaft 110.

Hereinafter, a circuit of the induction motor in accordance with theconventional art Will be described with reference to FIG. 2.

FIG. 2 shows a circuit of an induction motor in accordance with theconventional art.

As shown in FIG. 2, the circuit of the induction motor in accordancewith the conventional art includes: the main coils 160A and 160B and thesub-coils 160C and 160D connected in parallel with power terminals (Aand B); and a capacitor 200 electrically connected between a terminal(MAIN) of the main coils 160A and 160B and a terminal (SUB) of thesub-coils 160C and 160D.

A common terminal (COM) to which the main coils 160A and 160B and thesub-coils 160C and 160D are connected is electrically connected to thepower terminal (A), and the terminal (MAIN) of the main coils 160A and160B is electrically connected to the power terminal (B). In addition,in order to operate the induction motor with high efficiency, thewinding number of the main coils 160A and 160B and the sub-coils 160Cand 160D of the induction motor is designed so as to be suitable forhigh efficiency features. Namely, in order to operate the inductionmotor with high efficiency, the winding number of the main coils 160Aand 160B and the sub-coils 160C and 160D is determined according to thepower (AC).

Hereinafter, an operation of the induction motor in accordance with theconventional art will be described.

First, if the power (AC) is supplied to the power terminals (A and B),the power (AC) is applied to the main coils 160A and 160B, andsimultaneously to the sub-coils 160C and 160D through the capacitor 200.

Thereafter, a leading current with a 90 degree phase difference flows inthe sub-coils 160C and 160D by the capacitor 200, which causes the maincoils 160A and 160B and the sub-coils 160C and 160D of the stator 100 togenerate rotating magnetic fields.

The rotating magnetic fields generated by the main coils 160A and 160Band the sub-coils 160C and 160D are transmitted to the permanentmagnetic rotator 120, which leads the permanent magnetic rotator 120 tobe rotated. Namely, the induction motor according to the conventionalart is driven by generating driving torque through the capacitor 200 andthe sub-coils 160C and 160D.

However, the induction motor in accordance with the conventional art hasa problem: since the power (AC) is applied to the sub-coils 160C and160D and the main coils 160A and 160B, magnetomotive force is loweredwhen the induction motor is driven initially, and since themagnetomotive force is lowered, the induction motor cannot be swiftlydriven at the initial stage. That is, the induction motor according tothe conventional art is driven with high efficiency after its initialdriving, but it has a problem that the induction motor cannot be swiftlydriven due to the low magnetomotive force when the power is initiallyapplied to the induction motor. For example, when the voltage is appliedto the sub-coils 160C and 160D and the main coils 160A and 160B, theinduction motor is driven with high efficiency after its initialdriving. However, when the induction motor is initially driven, since acurrent less than required current for the driving is applied to thesub-coils 160C and 160D and the main coils 160A and 160D, themagnetomotive force is reduced. Thus the induction motor cannot beswiftly driven at the initial stage because the magnetomotive force isdecreased.

Meanwhile, the induction motor in accordance with the conventionalinvention is also disclosed in U.S. Pat. Nos. 6,700,270 and 6,445,092.

SUMMARY OF THE INVENTION

Therefore, an object of the present invention is to provide an inductionmotor controller which enables to swiftly drive the induction motor atthe initial stage.

Another object of the present invention is to provide an induction motorcontroller which enables to keep on driving the induction motor withhigh efficiency and low power consumption after swiftly driving theinduction motor at the initial stage.

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described herein,there is provided a motor controller including: a first capacitorconnected in series with a common terminal to which main coils andsub-coils of the motor are connected; and a PTC thermistor (PositiveTemperature Coefficient thermistor) connected in parallel with the firstcapacitor.

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described herein,there is provided an induction motor controller including: a firstcapacitor connected in series with a common terminal to which main coilsand sub-coils of the induction motor are connected; and a PTC thermistor(Positive Temperature Coefficient thermistor) connected in parallel withthe first capacitor.

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described herein,there is provided an induction motor including a stator having maincoils and sub-coils respectively wound around an iron core of theinduction motor, an induction rotor, a permanent magnet rotor installedbetween the rotor and the induction rotor, and a capacitor connected inseries between the main coils and the sub-coils, further comprising: afirst capacitor connected in series with a common terminal to which themain coils and the sub-coils are connected; and a PTC thermistor(Positive Temperature Coefficient thermistor) connected in parallel withthe first capacitor.

The foregoing and other objects, features, aspects and advantages of thepresent invention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention.

In the drawings:

FIG. 1 is a view schematically showing a construction of an inductionmotor in accordance with the conventional art;

FIG. 2 is a view showing a circuit of the induction motor in accordancewith the conventional art;

FIG. 3 is a schematic diagram showing a construction of an inductionmotor controller in accordance with a first embodiment of the presentinvention;

FIG. 4 is a graph showing operational characteristics of a PTCthermistor installed at the induction motor controller in accordancewith the first embodiment of the present invention;

FIGS. 5A and 5B are views showing an equivalent circuit of the inductionmotor controller in accordance with the first embodiment of the presentinvention;

FIG. 6 is a graph showing a change in a voltage applied to main coilsand sub-coils according to an operation of the induction motorcontroller in accordance with the first embodiment of the presentinvention;

FIG. 7 is a schematic diagram showing a construction of an inductionmotor controller in accordance with a second embodiment of the presentinvention; and

FIGS. 8A and 8B are views showing an equivalent circuit of the inductionmotor controller in accordance with the second embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, descriptions will now be made in detail to preferredembodiments of an induction motor controller which enables to swiftlydrive an induction motor at the initial stage and keep on driving theinduction motor with high efficiency and low power consumption afterswiftly driving the induction motor at the initial stage, referring toFIGS. 3 to 8B. Since a structure of the induction motor in accordancewith the present invention is the same as the conventional art, detaileddescription concerning it is omitted. Moreover, the same referencenumerals as the conventional art are used in the structure of theinduction motor of the present invention which is the same as that ofthe induction motor of the conventional art.

FIG. 3 is a schematic diagram showing a construction of an inductionmotor controller in accordance with a first embodiment of the presentinvention.

As shown in FIG. 3, the induction motor controller in accordance withthe first embodiment of the present invention includes a capacitor 202connected in series between a common terminal (COM) to which main coils160A and 160B and sub-coils 160C and 160D are connected in common, and apower terminal (A), and a PTC thermistor (Positive TemperatureCoefficient thermistor, PTC thermistor) 201 connected in parallel withthe capacitor 202.

Hereinafter, an operation of the induction motor controller inaccordance with the first embodiment of the present invention will bedescribed in detail.

Firstly, when the power (AC) is initially applied to power terminals (Aand B), the power (AC) is applied to the main coils 160A and 160B andthe sub-coils 160C and 160D only through the PCT thermistor 201.Operation characteristics of the PTC thermistor 201 will be describedwith reference to FIG. 4 as follows.

FIG. 4 is a graph showing operational characteristics of the PTCthermistor installed at the induction motor controller in accordancewith the first embodiment of the present invention.

As shown in FIG. 4, the PTC thermistor 201 has temperaturecharacteristics as follows: the PTC thermistor 201 has so low aresistance value when the power (AC) is initially applied to theinduction motor, and it has so high a resistance value when the power(AC) is applied to the induction motor for a predetermined time to heatthe PTC thermistor 201.

Accordingly, when the power (AC) is initially applied to the inductionmotor, since a resistance value of the PTC thermistor 201 is very low,the power is applied to the main coils 160A and 160B and the sub-coils160C and 160D only through the PTC thermistor 201.

An equivalent circuit of the induction motor controller according to theoperation of the PTC thermistor 201 will be described with reference toFIGS. 5A and 5B as follows.

FIG. 5A and 5B are views showing an equivalent circuit of the inductionmotor controller in accordance with the first embodiment of the presentinvention.

As shown in FIG. 5A, when the power (AC) is initially applied to theinduction motor, the resistance value of the PTC thermistor 201 is verylow. Therefore, the common terminal (COM) to which the main coils 160Aand 160B and the sub-coils 160C and 160D are connected in common isdirectly connected to the power terminal (A).

As shown in FIG. 5B, when the power (AC) is applied to the inductionmotor for a predetermined time, the PTC thermistor 201 is heated and thePTC thermistor 201 has so high a resistance value. Thus, the commonterminal (COM) to which the main coils 160A and 160B and the sub-coils160C and 160D are connected in common and the capacitor 202 areconnected in series. Namely, when the power (AC) is applied to theinduction motor for a predetermined time, since the PTC thermistor 201is turned-off, the power (AC) is applied to the main coils 160A and 160Band the sub-coils 160C and 160D only through the capacitor 202.

Hereinafter, a voltage applied to the main coils 160A and 160B and thesub-coils 160C and 160D according to an operation of the induction motorcontroller will be described in detail with reference to FIG. 6.

FIG. 6 is a graph showing a change in a voltage applied to the maincoils 160A and 160B and the sub-coils 160C and 160D according to theoperation of the induction motor controller in accordance with the firstembodiment of the present invention.

As shown in FIG. 6, when the power (AC) is initially supplied to theinduction motor, a high voltage is applied to the main coils 160A and160B and the sub-coils 160C and 160D. A high magnetomotive force isgenerated by supplying the high voltage to the main coils 160A and 160Band the sub-coils 160C and 160D. The induction motor is swiftly drivenat the initial stage by the high magnetomotive force.

In addition, after a predetermined time, if an operation of the PTCthermistor 201 is turned-off, the high voltage is reduced through thecapacitor 202 and the reduced voltage is applied to the main coils 160Aand 160B and the sub-coils 160C and 160D. Namely, if the operation ofthe PTC thermistor 201 is turned-off, the induction motor is driven(operated) with high efficiency and low power consumption by applying alow voltage to the main coils 160A and 160B and the sub-coils 160C and160D.

FIG. 7 is a schematic diagram showing a construction of an inductionmotor controller in accordance with a second embodiment of the presentinvention.

As shown in FIG. 7, the induction motor controller in accordance withthe second embodiment includes: a first capacitor 302 connected inseries between a common terminal (COM) to which the main coils 160A and160B and the sub-coils 160C and 160D are connected in common, and apower terminal (A); a PTC thermistor (Positive Temperature Coefficientthermistor, PTC thermistor) 303 connected in parallel with the firstcapacitor 302; and a second capacitor 301 connected in series with thePTC thermistor 303. Here, a capacity of the second capacitor 301 ishigher than that of the first capacitor 302.

Hereinafter, an operation of the induction motor controller inaccordance with the second embodiment of the present invention will bedescribed in detail.

Firstly, when the power (AC) is initially applied to the inductionmotor, since a resistance value of the PTC thermistor 303 is very low,the power (AC) is applied to the main coils 160A and 160B and thesub-coils 160C and 160D through the first capacitor 302 and the secondcapacitor 301. That is, a high voltage is applied to the main coils 160Aand 160B and the sub-coils 160C and 160D by a composite capacity of thesecond capacitor 301 and the first capacitor 302, so that the inductionmotor is swiftly driven at the initial stage.

Thereafter, after a predetermined time, if an operation of the PTCthermistor 303 is turned-off, the power (AC) is reduced through thecapacitor 302 is and the reduced voltage is applied to the main coils160A and 160B and the sub-coils 160C and 160D. Namely, if the operationof the PTC thermistor 303 is turned-off, the induction motor is driven(operated) with high efficiency and low power consumption by applying alow voltage to the main coils 160A and 160B and the sub-coils 160C and160D.

Hereinafter, an equivalent circuit of the induction motor controlleraccording to an operation of the PTC thermistor 303 will be describedwith reference to FIGS. 8A and 8B.

FIGS. 8A and 8B are views showing an equivalent circuit of the inductionmotor controller in accordance with the second embodiment of the presentinvention.

As shown in FIG. 8A, when the power (AC) is initially applied to theinduction motor, since a resistance value of the PTC thermistor 303 isvery low, the first capacitor 302 and the second capacitor 301 connectedin parallel with each other are connected to a common terminal (COM) towhich the main coils 160A and 160B and the sub-coils 160C and 160D areconnected in common. Namely, the power is applied to the main coils 160Aand 160B and the sub-coils 160C and 160D through the first capacitor 302and the second capacitor 301 connected in parallel with each other.Accordingly, a high voltage is applied to the main coils 160A and 160Band the sub-coils 160C and 160D by a composite capacity of the secondcapacitor 301 and the first capacitor 302, so that the induction motoris swiftly driven at the initial stage. Here, a voltage applied to themain coils 160A and 160B and the sub-coils 160C and 160D isproportionally increased according to a capacity of the first capacitor302 and that of the second capacitor 301.

As shown in FIG. 8B, when the power (AC) is applied to the inductionmotor for a predetermined time, since a resistance value of the PTCthermistor 303 is so high that the PTC thermistor 303 is turned-off, thefirst capacitor 302 is directly connected to the common terminal (COM)to which the main coils 160A and 160B and the sub-coils 160C and 160Dare connected in common. Namely, the power is reduced through the firstcapacitor 302 and the reduced power is applied to the main coils 160Aand 160B and the sub-coils 160C and 160D. Accordingly, the power isapplied to the main coils 160A and 160B and the sub-coils 160C and 160Donly through the first capacitor 302, so that the induction motor isdriven with high efficiency and low power consumption.

Meanwhile, in the present invention, in designing the main coils 160Aand 160B and the sub-coils 160C and 160D, it is preferable to determinethe winding number of the main coils 160A and 160B and the sub-coils160C and 160D according to the voltage reduced by the capacitors 202 and302.

As so far described in detail, the induction motor controller inaccordance with the present invention swiftly drives the induction motorat the initial stage by applying a high voltage to the induction motorat the initial stage.

In addition, the induction motor controller in accordance with thepresent invention can drive the induction motor with high efficiency andlow power consumption by applying a low voltage to the induction motorafter a predetermined time.

Further, since the induction motor controller in accordance with thepresent invention drives the induction motor with a low voltage after apredetermined time, the winding number of the main coils and thesub-coils of the induction motor can be reduced. Namely, as the voltageapplied to the main coils and the sub-coils is lowered, the windingnumber of the main coils and the sub-coils gets decreased.

As the present invention may be embodied in several forms withoutdeparting from the spirit or essential characteristics thereof, itshould also be understood that the above-described embodiments are notlimited by any of the details of the foregoing description, unlessotherwise specified, but rather should be construed broadly within itsspirit and scope as defined in the appended claims, and therefore allchanges and modifications that fall within the metes and bounds of theclaims, or equivalence of such metes and bounds are therefore intendedto be embraced by the appended claims.

1. A motor controller comprising: a first capacitor connected in serieswith a common terminal to which main coils and sub-coils of a motor areconnected; and a PTC thermistor (Positive Temperature Coefficientthermistor) connected in parallel with the first capacitor.
 2. The motorcontroller of claim 1, wherein, when the power is initially applied tothe motor, the power is applied to the main coils and the sub-coils onlythrough the PTC thermistor.
 3. The motor controller of claim 2, whereinthe power is applied to the main coils and the sub-coils only throughthe first capacitor after the power is applied to the motor for apredetermined time.
 4. The motor controller of claim 1, furthercomprising: a second capacitor connected in series with the PTCthermistor.
 5. The motor controller of claim 4, wherein a capacity ofthe second capacitor is higher than that of the first capacitor.
 6. Themotor controller of claim 5, wherein the power is applied to the maincoils and the sub-coils only through the first capacitor and the secondcapacitor after the power is applied to the induction motor for apredetermined time.
 7. An induction motor controller comprising: a firstcapacitor connected in series with a common terminal to which the maincoils and the sub-coils of the induction motor are connected; and a PTCthermistor (Positive Temperature Coefficient thermistor) connected inparallel with the first capacitor.
 8. The induction motor controller ofclaim 7, further comprising: a second capacitor connected in series withthe PTC thermistor.
 9. The induction motor including a stator havingmain coils and sub-coils respectively wound around an iron core of theinduction motor, an induction rotor, a permanent magnet rotor installedbetween the stator and the induction rotor, and a capacitor connected inseries with the main coils and the sub-coils, further comprising: afirst capacitor connected in series with a common terminal to which themain coils and the sub-coils are connected; and a PTC thermistor(Positive Temperature Coefficient thermistor) connected in parallel withthe first capacitor.
 10. The induction motor of claim 9, wherein, whenthe power is initially applied to the induction motor, the power isapplied to the main coils and the sub-coils only through the PTCthermistor.
 11. The induction motor of claim 10, wherein the power isapplied to the main coils and the sub-coils only through the firstcapacitor after the power is applied to the induction motor for apredetermined time.
 12. The induction motor of claim 9, furthercomprising: a second capacitor connected in series with the PTCthermistor.
 13. The induction motor of claim 12, wherein the power isapplied to the main coils and the sub-coils only through the firstcapacitor and the second capacitor after the power is applied to theinduction motor for a predetermined time.
 14. The induction motor ofclaim 13, wherein a capacity of the second capacitor is higher than thatof the first capacitor.